As shown in FIG. 6, a prior art small roller of the type described above comprises an elastic rubber cylinder 11, a metal cylinder 12 integral with the inner periphery of the rubber cylinder and a radial ball bearing 3 secured to the inner periphery of the metal cylinder, the ball bearing including an outer race 1 and an inner race 2 which is fixed to a shaft 4.
In this kind of small roller, smoothness in operation, reduction in vibration during operation and durability are particularly required. However, it is pointed out that in general, this kind of prior art small rollers do not always meet such requirements. In general, small rollers used in video tape recorders of VHS type have the outside diameter to the order of 12 to 13 mm and small rollers employed in video tape recorders of the 8 mm type have about 7.7 mm outside diameter.
To use a radial ball bearing 3 requiring an outer race 1 and an inner race 2 in such a small roller structure, a shaft 4 having a small diameter must be used for the structure. Further, these outer and inner races 1, 2, metal sleeve 12 and shaft 4 are a sliding fit instead of a press fit for the technical reason that when they are fitted together in accordance with a press fit method, the outer and inner races 1, 2 are caused to be deformed, resulting in changes in the inside diameter of the outer race 1 and the outside diameter of the inner race 2.
The sliding fit of those members can avoid such changes in the diameters that impart a vibration or rocking motion to the roller. However, it tends to cause a slippage between the sleeve 12 and the outer race 1 and a slippage between the inner race 2 and the shaft 4. Such a slippage is detrimental to ensuring smoothness of rotation of the roller and causes abrasive wear to the parts caused to be slipped. In addition, an error in the sliding fit of the parts that occurs from time to time during assembling work provides a cause for imparting to the roller a vibration or rocking motion which lowers durability of the roller.
Further, in video tape recorders, as it is inevitable that the motor-driven capstans against which a magnetic tape is pressed by pinch rollers are inclined to the order of 0.3.degree. with respect to their longitudinal axes for various technical reasons, it is necessary for the pinch rollers to have an automatic pressure regulating capability in order that they can be brought into pressure contact with the capstans over their entire length.
The radial ball bearing 3 employed in the prior art pinch roller is capable of being tilted for about 5.degree. at maximum with respect to the axis thereof and tends to cause the pinch roller to be excessively tilted. Such a tendency makes the pinch roller unstable in operation, whereby the tape to be transferred is, from time to time, caused to be biased during rotation of the roller. Furthermore, such a prior art pinch roller as mentioned above is constructed such that all the radial load is received only by the radial ball bearing and therefore lacks durable structure.